Improved resistance to cutting with a sharp edge has long been sought. Cut-resistant gloves are beneficially utilized in the meat-packing industry and in automotive applications. As indicated by U.S. Pat. Nos. 4,004,295, 4,384,449 and 4,470,251, and by EP 458,343, gloves providing cut resistance have been made from yarn which includes flexible metal wire or which consists of highly oriented fibers having high modulus and high tensile strength, such as aramids, thermotropic liquid crystalline polymers, and extended chain polyethylene.
A drawback with gloves made from yarn that includes flexible metal wire is hand fatigue with resultant decreased productivity and increased likelihood of injury. Moreover, with extended wear and flexing, the wire may fatigue and break, causing cuts and abrasions to the hands. In addition, the wire will act as a heat sink when a laundered glove is dried at elevated temperatures, which may reduce tensile strength of the yarn or fiber, thereby decreasing glove protection and glove life.
Improved flexibility and comfort and uncomplicated laundering are desirable in cut-resistant, protective apparel. Therefore, there is a need for a flexible, cut-resistant fiber that retains its properties when routinely laundered. Such a fiber may be advantageously used in making protective apparel, in particular highly flexible, cut-resistant gloves.
Polymers have been mixed with particulate matter and made into fibers, but not in a way that significantly improves the cut resistance of the fiber. For example, small amounts of particulate titanium dioxide has been used in polyester fiber as a delustrant. Also used in polyester fiber is a small amount of colloidal silicon dioxide, which is used to improve gloss. Magnetic materials have been incorporated into fibers to yield magnetic fibers. Examples include: cobalt/rare earth element intermetallics in thermoplastic fibers, as in published Japanese Patent Application No. 55/098909 (1980); cobalt/rare earth element intermetallics or strontium ferrite in core-sheath fibers, described in published Japanese Patent Application No. 3-130413 (1991); and magnetic materials in thermoplastic polymers, described in Polish Patent No. 251,452 and also in K. Turek et al., J. Magn. Magn. Mater. (1990), 83 (1-3), pp. 279-280.
Various kinds of gloves have been made in which metal has been included in the fabrication of the glove to impart protective qualities to the glove. For example, U.S. Pat. Nos. 2,328,105 and 3,185,751 teach that a flexible, X-ray shield glove may be made by treating sheets of a suitable porous material with a finely divided, heavy metal which may be lead, barium, bismuth or tungsten, or may be made from a latex or dispersion containing heavy metal particles. As illustrated by U.S. Pat. No. 5,020,161, gloves providing protection against corrosive liquids have been made with a metal film layer. These gloves also do not appear to have significantly improved cut resistance.
Aromatic polyamide fiber, commonly referred to as aramid fiber, has been used in protective apparel, such as bullet proof vests. One well known aromatic polyamide fiber, commercially available under the tradename Kevlar.RTM., is produced by the reaction of terephthalic acid and 1,4-phenylenediamine. While protective articles made with aramid fibers can exhibit desirable ballistic protection, such articles can be penetrated with sharp objects such as knives, i.e., such structures can exhibit poor cut-resistance.
Particles may be added to aramid fibers to increase the cut resistance thereof. See, for example, U.S. Pat. No. 5,738,940, hereby incorporated by reference, directed to particulate filled aromatic copolyamide fiber. However, the addition of particles to certain types of aromatic polyamide fibers can have a severe detrimental impact on fiber tensile strength. In particular, the addition of particles to "para-aramid" fibers, such as Kevlar.RTM., spun from lyotropic liquid crystal solutions, can significantly reduce the tenacity and elongation of the resulting fibers. It is believed the inclusion of such particles disrupts the liquid crystalline structure of the para-aramid fiber, thereby decreasing tensile strength. Still further, the presence of hard particles in aramid fibers generally can abrade downstream textile equipment.